/**
 * 对公众平台发送给公众账号的消息加解密示例代码.
 *
 * @copyright Copyright (c) 1998-2014 Tencent Inc.
 */

// ------------------------------------------------------------------------

package com.kr.weitao.util.wxencrypt;

import com.kr.weitao.exception.AesException;

import java.security.MessageDigest;
import java.util.Arrays;

/**
 * SHA1 class
 *
 * <p>计算公众平台的消息签名接口.
 */
class SHA1 {

  /**
   * 用SHA1算法生成安全签名
   *
   * @param token 票据
   * @param timestamp 时间戳
   * @param nonce 随机字符串
   * @param encrypt 密文
   * @return 安全签名
   * @throws AesException
   */
  public static String getSHA1(String token, String timestamp, String nonce, String encrypt) {
    StringBuffer hexstr = new StringBuffer();
    try {
      String[] array = new String[] {token, timestamp, nonce, encrypt};
      StringBuffer sb = new StringBuffer();
      // 字符串排序
      Arrays.sort(array);
      for (int i = 0; i < 4; i++) {
        sb.append(array[i]);
      }
      String str = sb.toString();
      // SHA1签名生成
      MessageDigest md = MessageDigest.getInstance("SHA-1");
      md.update(str.getBytes());
      byte[] digest = md.digest();
      String shaHex = "";
      for (int i = 0; i < digest.length; i++) {
        shaHex = Integer.toHexString(digest[i] & 0xFF);
        if (shaHex.length() < 2) {
          hexstr.append(0);
        }
        hexstr.append(shaHex);
      }

    } catch (Exception e) {
      e.printStackTrace();
    }
    return hexstr.toString();
  }
}
